Utilization of overvoltage and overcurrent compensation to extend the usable operating range of electronic devices

ABSTRACT

A method induces augmented levels of heat dissipation by exploiting quiescent IC leakage currents to control the temperature in high power devices. A heat control and temperature monitoring system (HCTMS) utilizes a thermal sensor to sense the junction temperature of a component, which becomes self-heated due to the quiescent leakage current inherent to the component upon the application of power to the component. By increasing the voltage level of the power source, this quiescent self-heating property is augmented, which serves to accelerate the preheating of the device, until the temperature rises above the minimum specified operating temperature of the component. The method further includes reliably initializing the system by applying full system power and triggering a defined initialization sequence/procedure. Once the component is operational, the method includes maintaining the component&#39;s temperature above the minimum operating threshold via continued self-heating, continued augmentation of the applied DC voltage, or both, where required.

PRIORITY CLAIM

The present application is a divisional of U.S. patent application Ser.No. 11/776,340, filed on Jul. 11, 2007 and titled “Utilization ofOvervoltage and Overcurrent Compensation to Extend the Usable OperatingRange of Electronic Devices,” the contents of which is incorporatedherein by reference.

RELATED APPLICATIONS

The present application is related to the subject matter of thefollowing co-pending applications, filed concurrently herewith andsimilarly assigned. The content of the related applications areincorporated herein by reference:

U.S. patent application Ser. No. 11/776,369, titled “System forExtending the Operating Temperature Range of High Power Devices;” and

U.S. Pat. No. 8,086,358 titled “Method for Pre-Heating High PowerDevices to Enable Low Temperature Start-Up and Operation.”

BACKGROUND

1. Technical Field

The present invention generally relates to electronic devices and inparticular to temperature control in electronic devices. Still moreparticularly, the present invention relates to leakage currents andtemperature control in electronic devices.

2. Description of the Related Art

When microelectronic devices are operated within the confines of theirstandard operating bias conditions, reliable performance is oftenrestricted to a limited temperature range. In addition, these devicesgenerally become unstable at low temperatures which limit the likelihoodof reliable system startup, causing improper initialization andoperation of the devices. As the technology evolves towards increasedcomplexity and faster speeds, power dissipation resulting from theincreased power densities of these devices become increasingly difficultto manage. The large amount of power (heat) dissipated by these complexdevices is due in part to high quiescent leakage currents that aremanifest by the large quantity and reduced lengths of parallel currentpaths inherent in the design of these devices. Excessive power levelslead to damaging high temperatures within the device, and coolingsystems are employed to prevent temperatures from reaching destructivelimits.

To further mitigate the problem of excessive power dissipation,operating voltages are reduced to a minimum value consistent withacceptable performance. However, this trend towards lower/minimumoperating voltages appears paradoxical since higher voltages often implyimproved performance due to higher noise margins. Thus, the useful rangeof function and performance is being traded off against reliabilitylifetime by restricting the limits of temperature and operatingvoltages. As operating voltages continue to be reduced in order tocounter increased device power dissipation from increased powerdensities, rapid convergence of these mitigating processes (of reducingoperating voltages and increasing power densities) towards a finitelimit is apparent. New designs are tasked with managing the delicatebalance between reducing operating voltages and increasing powerdensities to achieve increased functionality and/or performance over amaximized temperature range of reliable operation. As the trendcontinues, the balance becomes increasingly insurmountable and the rangeof reliable operation becomes proportionally more restricted.

BRIEF SUMMARY

Disclosed are a method and system for inducing and controlling the heatdissipated by leakage currents inherent to integrated circuits (ICs) toenable efficient attainment of a localized/junction temperature withinan operating temperature range for operation of high power devices. Inparticular, a heat control & temperature monitoring system (HCTMS)utilizes an attached or embedded thermal sensor to sense the junctiontemperature of a non-operating microprocessor or application specificintegrated circuit (ASIC). Upon the application of a power source, (forstart up initialization), the device becomes self-heated due to thequiescent leakage current inherent with the device. By increasing thevoltage level of the power source, this quiescent self-heating propertyis augmented which serves to accelerate the preheating or elevation ofthe temperature of the device, until the temperature, as measured by alocalized thermal sensor, rises above the minimum specified operatingtemperature of the device. The voltage level of the power source is thenrestored to a standard operating level. The device may then be reliablyinitialized by applying full system power, and triggering a hardwarereset or defined initialization sequence/procedure. Once the device isoperational, self-heating continues to maintain the device temperatureat or above the minimum operating threshold. In extreme cases, theaugmented voltage level is maintained, an ancillary heater is employed,or both mechanisms are concurrently applied to keep the device junctiontemperature in an operating temperature range.

The above as well as additional objectives, features, and advantages ofthe present invention will become apparent in the following detailedwritten description.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention itself, as well as a preferred mode of use, furtherobjects, and advantages thereof, will best be understood by reference tothe following detailed description of an illustrative embodiment whenread in conjunction with the accompanying drawings, wherein:

FIG. 1 depicts a high power device within which features of theinvention may be advantageously implemented;

FIG. 2 illustrates the heat control and temperature monitoring system(HCTMS) of a high power device in a feedback system, according to anillustrative embodiment of the present invention;

FIG. 3A depicts a negative field effect transistor (NFET) whichillustrates the generation of leakage currents, according to anillustrative embodiment of the present invention;

FIG. 3B depicts a positive field effect transistor (PFET) whichillustrates the generation of leakage currents, according to anillustrative embodiment of the present invention; and

FIG. 4 illustrates the process of applying increased/maximum operatingvoltages to augment a quiescent self heating mechanism (without anancillary heat source) to accelerate the attainment of temperaturelevels within the operating temperature range of high power devices,according to an illustrative embodiment of the present invention.

DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT

The present invention provides a method and system for inducing andcontrolling the heat dissipated by leakage currents inherent tointegrated circuits (ICs) to enable efficient attainment of alocalized/junction temperature within an operating temperature range foroperation of high power devices. In particular, a heat control &temperature monitoring system (HCTMS) utilizes an attached or embeddedthermal sensor to sense the junction temperature of a non-operatingmicroprocessor or ASIC (device). Upon the application of a power source,(for start up initialization), the device becomes self-heated due to thequiescent leakage current inherent with the device. By increasing thevoltage level of the power source, this quiescent self-heating propertyis augmented which serves to accelerate the preheating or elevation ofthe temperature of the device, until the temperature, as measured by alocalized thermal sensor, rises above the minimum specified operatingtemperature of the device. The voltage level of the power source is thenrestored to a standard operating level. The device may then be reliablyinitialized by applying full system power, and triggering a hardwarereset or defined initialization sequence/procedure. Once the device isoperational, self-heating continues to maintain the device temperatureat or above the minimum operating threshold. In extreme cases, theaugmented voltage level is maintained, an ancillary heater is employed,or both mechanisms are concurrently applied to keep the device junctiontemperature in an operating temperature range.

In the following detailed description of exemplary embodiments of theinvention, specific exemplary embodiments in which the invention may bepracticed are described in sufficient detail to enable those skilled inthe art to practice the invention, and it is to be understood that otherembodiments may be utilized and that logical, architectural,programmatic, mechanical, electrical and other changes may be madewithout departing from the spirit or scope of the present invention. Thefollowing detailed description is, therefore, not to be taken in alimiting sense, and the scope of the present invention is defined onlyby the appended claims.

It is also understood that the use of specific parameter names are forexample only and not meant to imply any limitations on the invention.The invention may thus be implemented with differentnomenclature/terminology utilized to describe the above parameters,without limitation.

With reference now to the figures, FIG. 1 depicts a system within whichfeatures of the invention may be advantageously implemented. System 100comprises temperature control sub-system 102. Temperature controlsub-system 102 comprises the following elements: (1) Thermal sensor 105;(2) Cooling system 103; and (3) heater 104. System 100 also comprisescomponents experiencing high levels of power dissipation (107),illustrated by high power component(s) 106. System 100 also comprisesvariable power supply 109. System 100 further comprises one or moredevices which experience quiescent leakage current when the devices areeither turned on but remain idle or are not operational. These one ormore devices may comprise transistors or other integrated circuitcomponents that exhibit the characteristics of generating heatdissipation due to leakage currents whenever power is applied toterminals of the devices, even when the device is itself still in the“off” (non-operational) mode. These devices may be sub-components ofhigh power components 106 and/or may also be (or be a part of) separate,non-high power components within the overall system 100. High powercomponents 106 are responsible for quiescent self heating, which (selfheating) is the result of the high power dissipation (107), and whichmay be due in part to leakage currents in electronic devices of the highpower components 106.

According to the illustrative embodiment, temperature control sub-system102 completes a series of functional processes using the componentswithin system 100, including: (1) monitoring a temperature and atemperature change of components 106 relative to a lowest operationaltemperature of components 106; (2) applying increased/maximum operatingvoltages to components 106 or sub-components within components 106 toinduce augmented levels of quiescent leakage currents to accelerate theelevation of temperature to within an operational range; (3) analyzingtemperature monitoring results to determine whether quiescent selfheating at specific temperatures is sufficient to efficiently andsingularly elevate an operational temperature of components 106; (4)utilizing the quiescent self heating properties of components 106without activating an ancillary heating source to maintain an operatingtemperature above the low operating temperature threshold; and otherfeatures/functionality described below and illustrated by FIGS. 2-4. Asfurther illustrated, temperature control sub-system 102 may also includemicrocode 108 (or operational logic), which activates the second, thirdand fourth functional features above, prior to and during systemoperation. This embodiment does not require, but also does not precludethe use of an ancillary heater (heater 104) which can be incorporatedwithin related alternate embodiments to aid in the acceleration,attainment, or maintenance of junction temperature above a lowestoperating temperature.

In temperature control sub-system 102, cooling components/system 103 isessentially coupled to thermal sensor 105. Cooling system 103 maycomprise a heat sink(s) and/or a cooling fan(s), for example. Thermalsensor 105 is also operationally coupled to high power (dissipating)components 106 of device 100. In one embodiment, thermal sensor 105 isan embedded thermal diode which measures the temperature of specificcomponents (among high power components 106) with reference to a lowoperational temperature threshold. The temperature detected by thethermal diode, i.e., the junction temperature, is determined bymeasuring a forward bias voltage of the diode which varies linearly withtemperature.

Thermal sensor 105 functions as a reliable thermal monitor prior to,during and after system startup, since thermal sensor 105 is capable ofaccurately reflecting the stabilized (average) system ambienttemperature prior to the application of system power. In addition,thermal sensor 105 provides a strategic monitor of maximum systemoperating temperature by virtue of its proximity to the high powerdissipation devices (for example, high power components 106) within asystem. While the illustrative embodiment is described with a thermaldiode providing the functionality of the device's thermalmonitor/sensor, many other types of devices may be utilized to providethe temperature monitoring function described herein, includingthermistors (temperature sensitive resistors), bimetallic thermocouplesor thermostats, et al., and the specific use/description of a thermaldiode is simply for illustration and not intended to be limiting on theinvention.

Heater 104 is placed substantially adjacent to thermal sensor 105, asillustrated in device 100. Heater 104 is only utilized as a back-upheating source to the self heating process in the initialization (startup) procedure when the temperature of high power component 106 withinsystem 100 is below the lowest operational temperature of the component.Thus, heat generated by/from heater 104 may be occasionally combinedwith the heat generated by the device's quiescent self heating processto preheat system 100 (and specifically high power components 106) up toa lowest operational temperature (of the components and/or system) inorder to accelerate the system start up process.

Before system 100 becomes operational, the temperature of components 106is raised to an operational temperature level. The self heating processresulting from leakage currents inherent to ICs is exploited in order toraise the temperature to an operational level of the components 106. Inorder to achieve a greater degree of self heating compared to the degreeof self heating attained with an applied standard operating voltage,variable power supply 109 is increased up to a limit specified as themaximum safe operating voltage for components 106. Increasing operatingvoltages to components 106 or sub-components within components 106induces augmented levels of quiescent leakage currents which acceleratesthe elevation of junction temperatures to within an operational range.Once components 106 attain operational temperature levels, system poweris applied and an initialization procedure commences, which concludeswhen the device becomes operational. When the device becomesoperational, the self heating process continues and may be singularlyused to maintain the device temperature above the lowest operationaltemperature.

The actual locations/positions of the above described components mayvary relative to each other, and the illustrative embodiment is providedsolely to illustrate one possible implementation and is not intended tolimit the invention to the illustrated configuration.

FIG. 2 illustrates the heat control and temperature monitoring system(HCTMS) of a high power device with feedback, according to anillustrative embodiment of the present invention. System 200 comprisesTemperature Control Subsystem (TCS) 201, which includes HCTMS controllogic 208, heater (H) 204, component (C) 206 and thermal sensor (S) 205(e.g., thermal diode). Heater (H) 204 is an ancillary heater that isconnected to and controlled (turned on/off) by HCTMS control logic 208.HCTMS control logic 208 is also connected to variable power supply 209,which controls the level of voltage power applied to thedevices/components within the system that generate/emit quiescent selfheat.

According to the illustrative embodiment, HCTMS control logic 208 isalso operationally coupled to voltage-to-temperature converter 210,which converts received electrical (current or voltage) output 220 fromthermal sensor 205 into the corresponding measured temperature ofcomponent 206. Converter 210 then provides the temperature value toHCTMS 208, which compares the measured voltage against presettemperature thresholds, such as the minimum temperature threshold andthe maximum temperature threshold of component 206. In one embodiment,converter 210 is provided as an internal logic within HCTMS controllogic 208 (as indicated by the dashed lines incorporating converter 210into HCTMS control logic 208). In another embodiment, converter 210 maybe logic within sensor 205 itself, rather than a separate component. Inyet another embodiment, no converter is utilized, and HCTMS controllogic 208 performs the comparison using the voltage/current values (220)received from thermal sensor 205.

Thermal sensor 205 monitors/detects junction temperature of component206 and provides an output 220 to converter 210, which output isindicative of the junction temperature. In one embodiment, thermalsensor 205 is a thermal diode and generates a voltage that isrepresentative of the present temperature of component 206. The voltagevalue (or corresponding current) output 220 generated by thermal sensor205 is fed into converter 210.

HCTMS control logic 208 is programmed with (or provided) a plurality ofcalibrated inputs, including the values of: (1) the minimum operatingthreshold temperature (T_(Min)) 212 (corresponding to the lowestoperational temperature threshold for component 206); (2) the maximumoperating temperature threshold (T_(Max)) 213 (corresponding to themaximum operational temperature of component 206); (3) the steady stageminimum voltage level for operating component 206 with minimal heatdissipation (V_(Min)) 214; and (4) the highest operational voltage levelthat should be applied across terminals of component 206 (V_(Max)) 215(corresponding to the voltage at which maximum heat dissipation occursfrom component 206 or surrounding devices).

The first two temperature values represent the operating temperaturerange of component 206. These values are utilized by HCTMS control logic208 to cause component 206 to attain the operational temperature beforeinitiating operation of component 206 and to maintain the temperature ofcomponent 206 within the operational range once component 206 becomesoperational. The two voltage values represent the operational voltagerange of component 206, with the first lower value, V_(Min) (214)representing the desired voltage for steady state operation of component206. The higher voltage value, V_(Max) (215) is utilized by HCTMScontrol logic 208 to provide enhanced pre-heating of component 206 toachieve the minimum operating temperature threshold beforeactivation/operation of component 206.

When the voltage (or temperature) output 220 from sensor 205 indicatesthat the measured junction temperature of component 206 is below theminimum operating temperature of component 206, HCTMS control logic 208triggers variable power supply 209 to increase the voltage being appliedto component 206. HCTMS control logic 208 triggers an increase in theapplied voltage up to V_(Max) so as to effect an increased and/or fasterheating of the junction temperature of component 206. Applying a largervoltage across component (or devices within or in vicinity ofcomponents) causes larger power dissipation due to quiescent leakage ofcomponent 206 (or devices), which leads to greater heat dissipation.

The variable power supply 209 may be triggered to increase the voltageacross the component by any value up to V_(Max), and actualdetermination of the amount of voltage increase may be performed bypre-analysis of the effects of voltage increase on the temperatureincrease around the component. The HCTMS control logic 208 may then becalibrated to provide just enough increase in voltage to effect theamount of pre-heating required/desired. In one embodiment, thecalibration may be a dynamic function, based on the feedback from sensor205 in response to measured increases in applied voltage. Thus, variableoutput 220 of sensor 215 is utilized to determine whether to continue(or initiate) pre-heating of the component by increasing the voltageprovided by variable power supply 209. Output signal 220 indicateswhether component 206 has attained the operational temperature andspecifically what temperature levels have been attained.

Control logic 208 determines, based on the temperatures attained bycomponent 206, whether to increase the operational voltage supplied tocomponent 206, which voltage is provided by variable power supply 209.This determination may be based on factors which may include ambientconditions and the rate at which self heating effectively raises thetemperature of component 206. For example, extremely low temperaturesmay dictate that a mid range operational voltage is attained before thevariable voltage supply is decreased/restored to a standard/nominaloperating voltage level. When the components have attained anoperational temperature, system power is applied to all key components,and the variable power supply is reduced to V_(Min). Subsequently, selfheating is relied upon for maintaining an operational temperature foreach key component, unless additional heating from heater 204 isrequired.

FIG. 3A depicts a negative field effect transistor (NFET) whichillustrates the generation of sub threshold leakage currents, accordingto an illustrative embodiment of the present invention. NFET 300facilitates an explanation of the heating impact of leakage currents inhigh power devices (e.g., components 106), which employ NFETs and othersemiconductor devices as integrated circuit (IC) building blocks. TheseICs may comprise millions of semiconductor devices.

NFET 300 comprises gate 301, source 303 and drain 302. A correspondinggate voltage (Vg) may be applied/connected to gate 301. A source voltage(Vs) may be applied/connected to source 303, and a drain voltage (Vd)may be applied/connected to drain 302. When the voltage applied at thegate of NFET 300 is high, i.e., the voltage level representing a digital“1”, NFET 300 is turned on and becomes operational. Alternatively, whenthe voltage applied at the gate of NFET 300 is low, i.e., the voltagelevel representing a “0”, NFET 300 is turned off and becomesnon-operational.

Because of small Metal Oxide Semiconductor Field Effect Transistor(MOSFET) geometries, high power devices are ideally designed to acceptvoltages at the gate, which voltages are small enough to allow thedevice to operate reliably. To maintain performance, the thresholdvoltage of the MOSFET is ideally small as well. As the threshold voltageis reduced, the transistor is incapable of being completely turned off;that is, the transistor operates in weak-inversion mode, with asub-threshold leakage, or sub-threshold conduction, between source anddrain. Thus, although NFET 300 may be turned off, a leakage current, forexample, leakage current 304, still flows.

High power ASICs and microprocessors, even when non-functional,dissipate a significant amount of heat due to leakage paths inherent inthe design. As microelectronic designs evolve, circuit geometries arereduced, leading to proportional increases in circuit density of ASICand microprocessor designs. In addition, the reduced geometries andsubsequent circuit densities result in shorter leakage paths inincreasing numbers per unit of volume. Consequently, higher powerdensities are found within the devices, such as components 106 (FIG. 1),as the microelectronic designs continue to evolve. Furthermore, thesehigh circuit density devices such as ASICs and microprocessors dissipatelarge amounts of heat due to the high density of leakage paths withinthe device. The leakage paths exist and are independent of the device'sfunctionality or performance. The level or amount of leakage current isproportional to some extent (or may be roughly correlated to) the sizeof the voltage applied across the device while the device is inquiescent stage. Also, the amount of heat dissipation due to the leakagecurrent is directly proportional to the amount of leakage current.

The heat generated by the leakage current effectively heats the device,i.e., quiescent self heating takes place. The high power dissipation dueto leakage path losses is utilized as a heat source of opportunity, and,as a heat source, is applied for the purpose of self pre-heating thedevice. This quiescent self pre-heating feature mitigates or reduces theneed for an ancillary pre-heat source which would otherwise be requiredto elevate the junction temperatures within the device to a temperaturewhich places the device within a reliable operating temperature range.

FIG. 3B depicts a positive field effect transistor (PFET) whichillustrates the generation of sub threshold leakage currents, accordingto an illustrative embodiment of the present invention. PFET 310comprises gate 311, source 312 and drain 313. A corresponding gatevoltage (Vg) may be applied/connected to gate 311. A source voltage (Vs)may be applied/connected to source 312, and a drain voltage (Vd) may beapplied/connected to drain 313. One of these voltages are higher thanthe other leading to a voltage drop across the device and subsequentcurrent flow through the device when the device is “on” or a leakagecurrent flow while the device is in quiescent stage. When the voltageapplied at the gate of PFET 310 is low, i.e., the voltage levelrepresenting a digital “0”, PFET 310 is turned on. Alternatively, whenthe voltage applied at the gate of PFET 310 is high, i.e., the voltagelevel representing a “1”, PFET 310 is turned off. The digital highvoltage level represents a voltage which is greater than the thresholdvoltage below which PFET 310 becomes operational. Thus, unlike NFET 300,PFET 310 is turned off when a digital 1 is applied to source 312.However, similar to NFET 300, leakage current 314 flows in PFET 310 whenthe device is turned off.

Microprocessors and large scale application specific integrated circuits(ASICs) comprise millions of semiconductor devices which, due to theirusage in any given design are not all in an off state when power isapplied and the device is quiescent or idle. Leakage current isincreased significantly due to the contribution of those cases where thesemiconductor devices are in an on state but nor operational (i.e., whenidle), lending to the high increase in power dissipation with increasingcircuit packaging densities.

FIG. 4 illustrates the process of increasing operating voltage toaugment a quiescent self heating mechanism (without an ancillary heatsource) for the purpose of attaining temperature levels within theoperating temperature range, according to an illustrative embodiment ofthe present invention. The process begins at block 401, and proceeds toblock 402, at which an activation procedure is initiated for some of thedevice's core components. The activation procedure is also responsiblefor initiating self heating via quiescent leakage current. In oneembodiment, the activation procedure may involve activating a systemstart up button, for example. Alternatively, a pre-programmed facilitymay initiate the device's activation procedure.

At block 403, the junction temperature corresponding to the high powercomponent(s) 106 is monitored using an embedded (or attached) thermalsensor (e.g. thermal sensor 105 of FIG. 1). In the illustrativeembodiment, where the embedded (or adjacent) thermal sensor of thecomponent (or a sensor embedded in an attached heat-sink) is a thermaldiode, the diode produces a forward bias voltage that varies linearlywith temperature. The diode is independent, and does not requireoperation of the system to provide this implicit temperaturemeasurement. The forward biased diode voltage that represents the lowestoperating temperature of the component(s) is determined throughcharacterization and/or calibration during or prior to a system designand/or final test. A comparator (threshold detector) switches its outputto indicate when the temperature of the high power component(s) attainsor goes above the lowest operating temperature of the component(s). Asdescribed above, the comparator may be internal logic of the HCTMScontrol logic.

At block 404, the applied power supply voltage is dynamically increasedto produce over-voltage (or over-current) and induce augmented selfheating via leakage currents. The application of over-voltage andover-current may be used to perform parametric drift compensation andalso serve as a self heat source of opportunity to elevate andaccelerate the rise in temperature when required to establish a reliabledevice operating temperature. The self heating process may also be usedto expand the usable operating range of microelectronic devices. Anexpanded operating temperature range is achieved by virtue ofconstructive compensation for out of tolerance parametric (voltageand/or current) shifts with decreasing temperature which would otherwisedegrade reliable operation in a typical and traditional applicationenvironment. The temperature increase realized in this manner is due tothe self heating of the device itself, induced and enhanced by theapplication of an increase in power supply voltage, and thus inputpower.

The applied voltage may remain at a higher than normal/standard valuefor as long as conditions for sustained and reliable functionality andperformance are maintained, and/or if the applied voltage is required tomaintain junction temperatures within prescribed or operational limitsor otherwise dictated to ensure reliable operation. The process ofinduced and augmented self heating proportionally increases thequiescent power dissipation, and thus junction temperatures within thedevice, to temperatures above that which would occur if operated withonly prescribed nominal/standard operating voltages and currentsapplied.

Power dissipation increases approximately by the square of the increasein applied operating voltage, and as long as safe operating limits aredefined and maintained, the process of increasing the applied voltageserves as a heat source of opportunity. The resulting quiescent selfheating proportionally increases the temperature of the device andfavorably compensates the internal operating junction temperatures whenvery low temperature operation is desired.

Returning to the figure, at block 405, a timer is initiated. The timeris used to track whether sufficient time, i.e., a preset amount of time,has elapsed in order to benefit from the (temperature elevating) impactof the quiescent self heating process. As leakage currents flow,quiescent self pre-heating begins/continues to elevate the junctiontemperature of the component, as shown at block 406. The temperaturecontrol logic then determines, at block 407, whether the junctiontemperature measured by the thermal sensor is, at least, equal to thelowest operational threshold temperature of the component. If thejunction temperature is less than the lowest operational thresholdtemperature of the device, the process moves to block 408, at which, thetemperature control system determines whether the preset time allowedfor preheating the component to an operational temperature (by applyingan increased voltage) has elapsed. If at block 408 the preset time haselapsed, the component is pre-heated utilizing an ancillary heat source(e.g., heater 104 in FIG. 1) in order to attain the lowest operationaltemperature, as shown at block 409. If at block 408 the preset time hasnot elapsed, quiescent self heating continues without the addition of anancillary heat source, as shown at block 406.

Returning to block 407, if the junction temperature is greater than orequal to the lowest operational threshold temperature of the device, thetimer is halted and the operating power supply voltage is restored to astandard operating level, as shown at block 410. Full system power isthen applied, accompanied by an initialization procedure which concludeswith the device (or component) being operational, as shown at block 411.

In one embodiment, previous results from a particular design and/orsystem test focused on power dissipation may be utilized to determinethe likelihood of success of quiescent self heating to elevate thetemperature of a specified device/component in certain ambientconditions. An expected degree/amount of quiescent self heating may bederived from empirical/test data, or from the results of productcharacterization performed by the device manufacturer. The quiescentself heating impact may also be time/age-correlated to the device.Extreme ambient conditions may trigger the immediate activation of anancillary heat source instead of waiting for the quiescent self heatingprocess to elevate the temperatures over a substantially large range.Thus, results from previous tests may be utilized by HCTMS 102 to makeappropriate and timely decisions and trigger specific actions.

Returning to FIG. 4, once the component is operational, the self heatingdue to the high power dissipation of components within the systemcontinues without an ancillary heat source to maintain the temperatureof the component within the operational temperature limits, as shown atblock 412. The component's temperature is continuously monitored by thethermal sensor and the self heating by the components enables thecomponent's temperature to remain above the operational threshold whilethe component remains operational. The power supply voltage may beincreased slightly or to the limit of maximum safe operating voltage,and in extreme cases, an ancillary heater may be activated when selfheating of the device under normal operating conditions is insufficientto maintain the device above the lowest operating temperature. Theprocess ends at block 413.

Thus, with the above embodiments, a system is provided having at leastone component that operates within a temperature range having a lowestoperating temperature. The system also has a temperature controlsubsystem having: (a) logic for detecting when a temperature of the atleast one component is below the lowest operating temperature; (b) logicfor triggering dissipation of heat by applying higher levels ofactivation power to devices within the system, which devices are proneto generate heat dissipation via quiescent leakage current. The higherlevels of activation power is applied by increasing the voltage abovethe normal operating voltage prior to applying system power to, andinitiating operation of, the at least one component. The higher levelsof activation power then enables the at least one component to bepre-heated to at or above the lowest operating temperature via the heatdissipation attributable to the quiescent leakage current; (c) logic forincreasing operating voltages to a maximum operating level to induceaugmented degrees of self heating; (d) logic for enabling an ancillaryheater when self heating of the device while operating under normaloperating conditions is insufficient to maintain the device above thelowest operating temperature; and (e) logic for enabling general systempower to be applied to the at least one component and subsequentoperation of the at least one component only when the temperaturemeasured at the at least one component is at or above the lowestoperating temperature.

In one embodiment, the devices to which activation power is applied maycomprise one or more transistors, which are initially in the off stateprior to application of general system power and which receives theactivation power across terminals and yields a quiescent leakage currentas a functional characteristic of the device and the applied voltagelevel.

More specifically, the logic for detecting comprises one or more thermalsensors that detect the temperature of the at least one component,wherein the one or more thermal sensors are calibrated to detect andgenerate an output indicative of the temperature of the component,including temperatures below the lowest operational temperature. Also,depending on the embodiment being implemented, the one or more thermalsensors may include at least one of: (a) one or more thermal diodeswhich produces a forward bias voltage which varies linearly withtemperature, wherein the diode is positioned proximate to the component;and (b) one or more thermistors; (c) one or more bimetallicthermocouples; and one or more thermostats.

Additionally, the logic for triggering dissipation of heat furthercomprises at least one heater that is selectively activated to generateheat for increasing the temperature of the at least one component whenheat dissipation from leakage current and self heating is not sufficientto raise or maintain a measured temperature above the lowest operatingtemperature. The device also comprises logic for activating the heaterwhen heat generated by leakage current heat dissipation does not elevatethe temperature of the at least one component above the lowestoperational temperature within a preset time period following a systemstart-up procedure that applies power to the devices without turning thedevices on. Then, when the detected temperature is at least equal to thelowest operational temperature threshold, the logic deactivates saidheater to allow self heating by heat dissipation of operating componentsand devices to maintain the operational temperature. However, when thedevice is operational and self heating is unable to maintain anoperational temperature, the logic automatically activates the heater toassist the self heating process in maintaining the operationaltemperature.

In one embodiment, the temperature control subsystem further comprises:logic for evaluating a temperature against pre-set criteria; and logicfor triggering activation of a selected one of multiple heating modesfrom among: (a) self heating using higher levels of applied power acrossdevices prone to quiescent current leakage, without use of an ancillaryheater, wherein heat dissipation from the devices and components is usedas a singular heating source during system operation, without activatingthe ancillary heater to maintain the operating temperature within saidoperating temperature range; (b) self heating along with use of theancillary heater when the self heating is not sufficient to maintain thetemperature of the at least one component above the lowest operatingtemperature; and (c) combined heating via self heating and use of theancillary heater to enable initialization of the at least one component,maintain operation of the at least one component once initialized, andextension of the operating temperature range of the at least onecomponent below a normal lowest ambient temperature surrounding thesystem.

In another embodiment, when greater control of the induced and augmentedself heat-generation process is required, an increase of the operatingvoltage may be executed in one of the following ways: (1) applying afixed preset increase of the operating voltage level; and (2) adaptivelyadjusting the applied operating voltage while the junction temperatureswithin the device are continuously monitored.

Finally, in one embodiment, a method is provided for pre-heating adevice with one or more components. The method comprises: initiating atimer when increased system power is applied to trigger pre-heating viaincreased quiescent leakage current; determining an elapsed timeinterval following initiation of the timer; monitoring an impact of heatdissipation caused by the increased quiescent leakage current on anincrease in detected temperature within a pre-defined interval; and whenthe impact is less than a pre-set level of increased temperature of thedevice (or component) required within the pre-defined interval,activating an embedded heater to enhance the rate of temperatureincrease until the detected temperature is at or above the operationaltemperature.

While the invention has been particularly shown and described withreference to the illustrated embodiments, it will be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the invention.For example, other mechanisms for detecting ambient heat other than theuse of thermal diodes may be provided in alternate embodiments.

What is claimed is:
 1. A method for controlling operating temperature of high powered devices, the method comprising: monitoring a temperature of one or more components of an electronic device relative to a lowest operating temperature threshold for the one or more components; prior to applying system power to and initiating operation of at least one component that has a temperature below its lowest operating temperature threshold, triggering an application of activation power to one or more other components that exhibit leakage characteristics resulting in heat dissipation via quiescent leakage current, wherein the at least one component is heated, via the quiescent leakage current heat dissipation, to a temperature that is at or above the lowest operating temperature threshold for that component; in response to detecting that one or more junction temperatures within the device are below the operational level, increasing the power supply voltage level to one of a maximum operating level and a preset offset below the maximum operating level, in order to increase a rate of self heat dissipation; restoring the power supply voltage to an optimal operating level and initializing the processor device in response to the junction temperatures reaching or being above the operational temperature threshold; and enabling general system power to be applied to the at least one component and subsequent operation of the at least one component only when a measured temperature of the at least one component is at or above the lowest operating temperature.
 2. The method of claim 1, wherein: said monitoring is completed via one or more thermal sensors that detects the temperature of the at least one component, wherein the one or more thermal sensors are calibrated to detect and generate an output indicative of the temperature of the component, including temperatures below the lowest operating temperature threshold; and wherein the one or more thermal sensors includes at least one of: one or more thermal diodes which produces a forward bias voltage which varies linearly with temperature, wherein the diode is positioned proximate to the at least one component; one or more thermistors; one or more bimetallic thermocouples; and one or more thermostats.
 3. The method of claim 1, wherein said increasing the power supply voltage level further comprises: in response to requiring greater control of the self-heating being generated, executing one of the following: applying a fixed preset increase of the operating voltage level; adaptively adjusting the applied operating voltage while continuously monitoring the junction temperatures within the device.
 4. The method of claim 1 further comprising: triggering the activation of an ancillary heater to elevate the temperature of the at least one component above the lowest operating temperature within a preset time period following a system start-up procedure that applies power to the components without turning the devices on, in response to an accelerated and an augmented heating rate being required compared with the heat generated by quiescent leakage current heat dissipation; and in response to a detected temperature being at least equal to the lowest operating temperature threshold when an ancillary heater is currently active, deactivating said ancillary heater to allow self heating by heat dissipation from operating components and devices to maintain the operational temperature.
 5. The method of claim 1, wherein said triggering further comprises: initiating a timer in response to application of the activation power to trigger pre-heating via the quiescent leakage current; determining an elapsed time interval following initiation of the timer; monitoring an impact of heat dissipation caused by the quiescent leakage current on an increase in detected temperature within a pre-defined interval; and in response to the impact being less than a pre-set level of increased temperature of the one or more components desired within the pre-defined interval, activating an embedded heater to enhance the rate of temperature increase until a detected temperature is at or above the operational temperature.
 6. The method of claim 1, wherein said enabling further comprises: executing an initialization procedure in which the system becomes operational when the temperature of the one or more components reaches at or above the lowest operating temperature; maintaining the temperature of the one or more components within operational temperature limits utilizing self heating by the devices and one or more components and cooling via a cooling mechanism of the system; and in response to the temperature of the one or more components falling to within a pre-set range of the lowest operating temperature, selectively activating an embedded heating source to combine heat generated from the embedded heating source with the heat generated by self heating to maintain the temperature of the component within the operating temperature range. 